United States Department of Defense
The United States Department of Defense, also known as the DoD, is a department in the United States government that is in charge of the military of the United States. It was created in 1947 and its headquarters is in The Pentagon in Washington, D.C.. The person in charge of the Department of Defense is called the Secretary of Defense. The current Secretary of Defense is James Mattis, who replaced Ash Carter in 2017. The Secretary of Defense answers directly to the President.
The Department of Defense is made up of the Department of the Army, the Department of the Navy, the Department of the Air Force, the National Security Agency, and the Defense Intelligence Agency. (The Department of the Navy includes the Navy and the Marine Corps. Also, during time of war the United States Coast Guard is under the authority of the Department of Defense.)